April 30, 2012

Flux

Aral Sea shrinks, central Asia

The Aral Sea, located in Kazakhstan and Uzbekistan in central Asia. Left: June 4, 1977. Center left: September 17, 1989. Center right: May 27, 2006. Right: June 3, 2009. Once one of the largest inland bodies of salty water in the world and the second largest sea in Asia — 70,000 square kilometers or 27,000 square miles in area — the Aral Sea has shrunk dramatically over the last 30 years. One of the main reasons is crop irrigation: water has been drawn off from the rivers that kept the Aral Sea filled. As the sea has shrunk, the local climate has become harsher, there have been contaminated dust storms, and drinking water and the local fishing industry have been lost. By the late 2000s, the Aral Sea had lost four fifths of its water volume.

I just came across another extraordinary internet resource courtesy of NASA (whose captions and credits are quoted throughout). Titled “State of Flux – Images of Change,” it currently contains close to two hundred images of changes to the surface of our planet over the last few decades – it makes for mesmerising browsing. It comes under “climate.nasa.gov” but it’s by no means only about climate change – it chronicles other natural processes together with the – often depressing – footprints of our species. I found the site through a Scientific American blogpiece titled “Views from Space show a Fragile Earth.” I must admit that I find this a strange title, an example of the emotional use of the word “fragile". This planet has been around, perfectly successfully and robustly, for 4.5 billion years – fragile it ain’t. The fragility of our own precarious and short-lived perch on the planet is another thing – and, in reality, what is being referred to by the adjective. But I am not setting up my soap-box here – the point is to celebrate the technology, and the access to it, that NASA offers. And yes, celebrate – we may, as many of these images provocatively show, be screwing around with the current nano-frame of the planet’s biopic, but at least we can’t hide that fact.

The following images are simply a personal selection after an initial browse, starting with the classic at the head of this post; further comment is hardly necessary.

River changes, China

The Yellow River Delta in China. Left: 2001. Right: 2009. The Yellow River is the second-longest river in China, and the sixth-longest in the world. It has been the cradle of Chinese civilization; but frequent devastating floods have also earned it the name of "China's Sorrow." Historical maps tell us that the river has undergone many dramatic changes in its course. Currently, the Yellow River ends in the Bohai Sea, yet its eastern terminus continues to oscillate from points north and south of the Shandong Peninsula. These images show the changes.

Dakhla Oasis, Egypt. Left: January 4, 1986. Right: January 14, 2010. Dakhla Oasis lies 300 kilometers (190 miles) west of the Nile. It is surrounded by the driest of desert landscapes, but beneath it lies the southern edge of the Post Nubian Aquifer. Use of water drawn from deep wells in the aquifer has increased tenfold since 1960, with a corresponding growth in agriculture. But some studies suggest that the planned rate of extraction is unsustainable and will lead to local depressions in the water table, making the precious liquid more and more expensive to access.

The Omo Delta, at the north end of Lake Turkana, a lake now located mainly in Kenya. Left: February 1, 1973. Right: January 24, 2005 to February 12, 2006. In 1973, the delta was contained entirely within the boundaries of Ethiopia. By 2005-2006, the southernmost point of the delta had moved roughly 12 kilometers (7 miles) to the south, and had crossed the Ethiopia-Kenya border. Reduced lake levels — from less rain, more diverted upstream water, and increased evaporation due to higher temperatures — are believed to be the primary cause, with an increase in sediment from agricultural activities also contributing. The expanded delta has provided new land for 20,000 Dassanech people, the area?s traditional inhabitants. But severe flooding in 2006 killed 100 of them and destroyed houses, crops and infrastructure.

Toshka, Egypt. Left: September 13, 1984 to September 29, 1987. Center: August 23 to September 1, 2000. Right: March 21 to 28, 2010. In the mid-1990s, excess water was channeled from the Lake Nasser reservoir on the Nile River to the Toshka Depression in the Western Desert, creating a series of lakes. This "New Valley Project" was to relieve overcrowding within the Nile Valley and boost the economy. Despite soil poorly suited to irrigation, the area produced grapes, cantaloupes, tomatoes, cucumbers, citrus fruits and wheat. But Lake Nasser water levels fell after 1998 and flow to Toshka ceased in 2001. At the current rate of decline, the new lakes will be lost to evaporation within the next few years.

The Atacama Desert, Chile. Left: November 23, 1987. Right: June 25, 2009. Population has doubled here over the past two decades due to explosive tourist development in the 1990s and a mining boom in the 1980s, when companies began to extract lithium and other minerals from the Atacama Salt Flats. Today the mining, tourism, domestic and agricultural sectors compete for the region's resources, and the main source of conflict is access to water. These images show the growth of mining operations from their beginning (white rectangle at lower right of the 1987 image) to a more recent level (purple and while rectangles in the 2009 image).

Left: January 12, 1976. Right: February 2, 2007. Baban Rafi Forest is the most significant area of woodland in the Maradi Department of Niger, a west African country on the southern edge of the Sahara Desert. Located at the southern extreme of the Sahel, Baban Rafi has areas of both savannah and Sahelian vegetation. These pictures show the loss of a significant fraction of the natural landscape (darker green areas) of the forest to agriculture. Population in this region quadrupled during the 40 years leading up to the 2007 image, and intense demand for agricultural land has led to near-continuous use, with shortened or no fallow period to recover fertility. The remaining woodlands are overly exploited for fuel wood and non-wood forest products.

Jakarta, Indonesia. Left: 1976, with a population of six million. Middle: 1989, with nine million inhabitants. Right: 2004, with 13 million inhabitants. Jakarta was the last Hindu kingdom of West Java when the Portugese arrived in 1522. They were driven out 5 years later by Muslim saint and leader Sunan Gunungjati, who renamed the city Jayakarta. In the 17th century the Dutch captured the city, fortified and walled it, and renamed it Batavia. After World War II, Dutch colonial power came to an end when Soekarno declared the Republic of Indonesia. This time series of images shows the growth of the city over the past few decades; vegetation is rendered in red and urban areas shown in blue-grey.